The invention relates to a fuel supply system for an internal combustion engine.
The invention can be applied in connection with internal combustion engines installed in automotive vehicles, especially in heavy-duty vehicles, such as trucks, buses and construction equipment, or with internal combustion engines in fixed installations.
It is common for internal combustion engines to have high pressure injections systems where fuel is first pressurized by a so-called low pressure pump and then pressurized to a higher pressure level by one or several high pressure pumps before being injected in the cylinders of the internal combustion engine. In such systems, the low pressure pump delivers fuel to a low pressure supply circuit having at least one delivery connection to the high pressure circuit(s).
Document US-2004/0261772 describes such a system. In that system, the low pressure pump delivers fuel to a fuel gallery in which fuel pressure is regulated by a pressure regulator under the form of a combination valve. At the output of the pressure regulator, the fuel is returned to the low pressure pump via a return line without passing through the fuel tank. In such a system, it is possible to have a high recirculation rate of fuel in the low pressure supply circuit without systematically returning to the tank all the fuel recirculated. This avoids the need for the recirculated fuel to pass through the primary filter which is installed between the tank and the low pressure pump input. In the system of document US-2004/0261772, a vent line is provided which is connected to the tank. The vent line is not pressurized.
In some cases, the high pressure circuit(s) contains one or several high pressure pumps which absorb fuel in such a way that it may generate pressure variations or pulses in the low pressure supply circuit. These pressure variations or pulses may have negative effects. Also, due to the fact that the recirculated fuel goes directly back to the low pressure pump without passing through the tank, heating up of fuel at engine started is quicker. However, in certain operating conditions, the temperature of fuel circulating in the low pressure supply circuit may be somewhat too high.
It is desirable therefore to improve the above type of fuel supply circuit.
According to an aspect of the present invention, a fuel supply system for an internal combustion engine is provided comprising:                a low pressure fuel pump to be fluidically connected to a fuel feeding circuit (12) to receive fuel from a fuel tank;        a low pressure supply circuit through which fuel is delivered by the low pressure pump to one or several high pressure circuits, said low pressure supply circuit comprising at least one delivery connection for delivering fuel to the high pressure circuit(s);        a pressure regulator which has an input fluidically connected to the low pressure supply circuit and an output which is fluidically connected to a pump return circuit in order that excess fuel from the low pressure supply circuit (34) is discharged through the pressure regulator in the pump return circuit, wherein the pump return circuit is fluidically connected to an input of the low pressure pump without passing through the fuel tank;        
characterized in that the pressure regulator is located downstream of the at least one delivery connection to the high pressure circuit(s), and in that a fuel derivation circuit is fluidically connected to the low pressure fuel supply circuit at a derivation pick-up location downstream of the at least one delivery connection to the high pressure circuit(s) and upstream of the pressure regulator.
According to further optional features of the invention, some of which may be combined:                in normal operation of the fuel supply system, a continuous flow of pressurized fuel is circulated in the fuel derivation circuit; The pressure being maintained in the derivation circuit at a pressure above atmospheric pressure, preferably at least one bar above atmospheric pressure, fuel circulation is warranted.        the low pressure fuel supply circuit may comprises at least two delivery connections to the high pressure circuit(s) associated to different high pressure pumps, and the derivation pick-up location is located downstream of the at least two delivery connections to the high pressure circuit(s).        the low pressure supply circuit may comprise at least one fuel retrieval connection to the high pressure circuit(s) where fuel from the high pressure circuit(s) is recovered in the low pressure fuel supply circuit, and the pressure regulator may be located downstream of the at least one retrieval connection to the high pressure circuit(s).        the fuel derivation circuit may be fluidically connected to the low pressure fuel supply circuit at a derivation pick-up location which may be both downstream of the at least one delivery connection to the high pressure circuit(s), and downstream of the at least one retrieval connection to the high pressure circuit(s).        the low pressure supply circuit may comprise at least one gallery which is thermally connected to an engine block or to an engine cylinder head, and the derivation pick-up location is located downstream of the gallery.        the gallery may be formed in the engine block or in the engine cylinder head.—the fuel derivation circuit may have a derivation flow limiter. The derivation flow limiter may be located at a distance from the derivation pick-up location, for example at least 50 centimetres from the derivation pick-up location. The pressure of fuel in the derivation circuit, upstream of the derivation flow limiter, may be superior to the atmospheric pressure. It may be in the range of 1 to 10 bars above atmospheric pressure, preferably in the order of 1 to 5 bars above atmospheric pressure.        the fuel derivation circuit may direct fuel to the fuel tank.        the fuel system may comprise at least one filter and a filter heating circuit, and the fuel derivation circuit may direct fuel to the filter heating circuit.        the fuel derivation circuit may direct fuel both to the fuel tank and to the filter heating circuit.        the fuel derivation circuit may comprise a tank return flow limiter and the filter heating circuit may be fluidically connected to the fuel derivation circuit upstream of the tank return flow limiter.        the filter heating circuit may have a heating circuit flow limiter.        the fuel derivation circuit may have a check valve for preventing fluid flow from the fuel derivation circuit back to the low pressure supply circuit.        the check valve may be located upstream of a flow limiter in the fuel derivation circuit.        the filter heating circuit may be fluidically connected to the fuel derivation circuit downstream of the check valve for preventing fluid flow from the fuel derivation circuit back to the low pressure supply circuit.        the fuel from the filter beating circuit may be circulated through the filter:        the fuel from the filter heating circuit may be circulated proximate the filter.        the filter may be a primary filter located in the fuel feeding circuit upstream of the low pressure pump.        the fuel system may comprise comprises a fuel feed pump in the fuel feeding circuit for delivering fuel to the low pressure pump.        
According to another aspect of the present invention, an internal combustion engine arrangement is provided comprising a fuel supply system including any of the above teatimes.
According to another aspect of the present invention, a vehicle equipped with an internal combustion engine arrangement is provided including any of the above features.
Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims.